0620 w15 ms 33 - GCE Guide

CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International General Certificate of Secondary Education

MARK SCHEME for the October/November 2015 series

0620/33

0620 CHEMISTRY

Paper 3 (Extended Theory), maximum raw mark 80

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners' meeting before marking began, which would have considered the acceptability of alternative answers.

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers.

Cambridge will not enter into discussions about these mark schemes.

Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE?, Cambridge International A and AS Level components and some Cambridge O Level components.

? IGCSE is the registered trademark of Cambridge International Examinations.

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Mark Scheme Cambridge IGCSE ? October/November 2015

Syllabus Paper

0620

33

Abbreviations used in the Mark Scheme ? ; separates marking points ? / separates alternatives within a marking point ? () the word or phrase in brackets is not required but sets the context ? A accept (a less than ideal answer which should be marked correct) ? I ignore (mark as if this material were not present) ? R reject ? ecf credit a correct statement that follows a previous wrong response ? ora or reverse argument ? owtte or words to that effect (accept other ways of expressing the same idea)

? Cambridge International Examinations 2015

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Mark Scheme Cambridge IGCSE ? October/November 2015

Syllabus Paper

0620

33

Question

Answer

1(a) cobalt chloride (paper) / anhydrous cobalt chloride / CoCl 2; from blue; to pink; or copper sulfate / anhydrous copper sulfate / CuSO4; from white; to blue;

1(b) boils at 100 ?C / boiling point 100 ?C / freezes at 0 ?C / freezing point 0 ?C / melts at 0 ?C / melting point 0 oC;

1(c) any two from: ? filtration / sedimentation / sieving / screening / (pass through) gravel (beds) / flocculation / decantation / clarification / coagulation / flotation / settling tank / add aluminium sulfate; ? (add) carbon; ? chlorination / (add) chlorine / add Cl 2; ? fluoridation / add fluoride; ? ozone dosing; ? desalination; ? aeration; ? distillation;

1(d) any two from: making steel; making paper; textiles; generating electricity / energy / power / turbines; HEP; water mills; steam power (e.g. steam engines); geothermal power; agriculture; livestock; irrigation; hydration of alkenes / manufacture of ethanol / alcohols; manufacture of sulfuric acid / Contact process; manufacture of hydrogen; solvent / dissolving; coolant / cooling; cleaning / washing; (supply of) drinking (water); central heating; production of slaked lime; cooking;

Marks 3

1 2

2

? Cambridge International Examinations 2015

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Question 2(a) sulfur dioxide / SO2; 2(b) hydrogen / H2; 2(c) ethene / C2H4; 2(d) argon / Ar; 2(e) carbon monoxide / CO; 2(f) methane / CH4;

Mark Scheme Cambridge IGCSE ? October/November 2015

Answer

Syllabus Paper

0620

33

Marks

1 1 1 1 1 1

Question

Answer

3(a)(i) 3(a)(ii) 3(a)(iii) 3(b)(i) 3(b)(ii) 3(b)(iii)

3(b)(iv)

vibrate (about fixed position) / vibration;

electrostatic force of) attraction; (between) positive ions and negative ions / oppositely charged ions / unlike charged ions / cations and anions;

regular / repeated / pattern / framework / ordered / alternating / organised (arrangement of); positive and negative ions / oppositely charged ions / cations and anions / unlike charged ions;

correct direction (going towards negative electrode);

Li+ + e? Li / Li+ Li ? e?;

2Br? Br2 + 2e? / 2Br? ? 2e? Br2 formulae; balancing;

Br? / bromide (ion); electron lost / donated electrons / increased oxidation state / increased oxidation number / oxidation numbers changed from ?1 to 0 / increased valency;

Marks

1 1 1 1 1 1 1 2

1 1

? Cambridge International Examinations 2015

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Mark Scheme Cambridge IGCSE ? October/November 2015

Question

Answer

3(c) M1 (gas) hydrogen (given off at cathode) / H2; M2 hydroxide ions / lithium hydroxide / OH? / LiOH are alkali(ne);

M3 2LiBr + 2H2O 2LiOH + H2 + Br2; or 2H+ + 2e? H2 / 2H+ H2 ? 2e?; or 2Br? Br2 + 2e? / 2Br? ? 2e? Br2; or 2H+ + 2Br? H2 + Br2;

Syllabus Paper

0620

33

Question

Answer

4(a)(i)

4(a)(ii) 4(a)(iii) 4(b)(i)

4(b)(ii)

any three from: ? (same) general (molecular) formula; ? (consecutive members) differ by CH2; ? same functional group; ? common (allow similar) methods of preparation; ? same / similar chemical properties / (chemical) reactions;

CnH2n CnH2n+2

alkene; alkane;

alkanes all or only (C?C) single bonds / no double bonds / no multiple bonds; alkenes (at least one) C=C / double bond / multiple bond;

heat / high temperature / temperature between 450 ?C and 800 ?C; catalyst / named catalyst, e.g. zeolites or alumina or aluminium oxide or aluminosilicates or silica or oxides of chromium; or high pressure / pressure in range of 2?70 atm; or steam; absence of air / oxygen;

any correct equation producing an alkane and an alkene adding up to seven carbon atoms in the products;

? Cambridge International Examinations 2015

Marks 3

Marks 3

1 1 1 1 2

1

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